1. Field of the Invention
The present invention relates to a spin transistor, and more particularly to a spin transistor which receives spin information through a source using a strong stray magnetic field generated by a ferromagnetic material, adjusts a spin orientation by the control of a gate, and selectively outputs electrons in a desired spin orientation through a drain.
2. Description of the Related Art
Today, a representative element of integrated circuit (IC) technology is based on a metal oxide semiconductor field effect transistor (MOSFET). A memory element such as DRAM or flash memory, an application specific integrated circuit (ASIC), a microprocessor, or a logic circuit includes a MOSFET for ON/OFF switching operation as a basic component. Recently, a new concept element which is widely studied is a spin field effect transistor (spin-FET). Whereas only charges in semiconductor are controlled using an electric field in the existing semiconductor-based transistor, charges and spin are simultaneously controlled in the spin transistor. The spin transistor can be used as a switching element and a logic circuit by controlling spin-polarized electrons.
In the MOSFET currently being used as an important element in the semiconductor field, power consumption and area will be hardly reduced. The MOSFET is confronted with a physical limitation of an oxide layer. In order to solve such problems, spin precession of the electrons is controlled by a voltage. The spin transistor includes a source, a drain, and a channel for connecting them. The channel of the spin transistor may be a two-dimensional electron channel layer.
However, in a conventional spin transistor (for example, see Datta-Das spin transistor (Applied Physics Letters, vol. 56, 665, 1990) or a magnetic spin injected field effect transistor disclosed in U.S. Pat. No. 5,654,566), spin information needs to be injected from a ferromagnetic material to a semiconductor or from a semiconductor to a ferromagnetic material. However, the semiconductor and the ferromagnetic material, including metal, are significantly different from each other in electric conductivity. Thus, the injection efficiency of the spin information is very low. That is, the information may be lost when passing through a junction surface therebetween and thus a clear signal is difficult to obtain from the spin transistor.